京津冀地区中α尺度飑线过程中大风特征分析及成因初探     

吴紫煜  姚雯  李超 《气象与环境科学》2016,39(2):90-98

应用常规天气观测资料、地面加密自动气象站资料、大风灾情报资料、京津冀地区7部多普勒天气雷达组网观测资料及VDRAS资料,从多个角度对2013年8月4日京津冀地区一次飑线过程产生的大范围大风天气过程进行了分析,结果显示:此次过程是在高空冷空气南下、低层暖湿气流北上、系统前倾及位势不稳定的有利层结条件下,由多单体风暴演变为中α尺度的强飑线所致。飑线形成于低层垂直切变加强、冷池合并之后;大风主要发生在飑线主体回波中,其次是主体回波前和中前,主体回波后很少发生。大风发生的位置取决于飑线结构中气流的性质,气流的性质与冷池前进的程度和对流的强度关系密切。大风大部分由下沉冷气流产生,少数为近地面上升暖气流导致。大风发生的范围和强度与低层风垂直切变的强度呈正比,大范围低层风垂直切变的加强增强了飑线入流和出流的强度,是大范围大风、局部强风形成的重要原因。大风发生站次与冷池的强度和范围密切相关,冷池的加强和范围的扩大加强了后侧冷入流和前侧暖入流的强度和范围,也是大范围大风形成的重要因素。  相似文献   

耦合长期预报的跨流域引水受水水库调度模型          下载免费PDF全文

卢迪  周如瑞  周惠成  彭勇 《水科学进展》2016,27(3):458-466

为提高跨流域引水工程受水水库引水有效性,研究了耦合长期径流预报信息的跨流域引水受水水库调度模型。首先选取汛期径流预报信息,采用径流预报概率修正先验概率来描述径流的不确定性,建立了贝叶斯随机动态规划模型(BSDP-LTF)。然后将模型应用于碧流河水库,并与仅考虑径流相关的随机动态规划模型(SDP-I)、仅考虑长期预报信息的随机动态规划模型(SDP-LTF)进行比较。比较结果得出在供水保证率基本一致且不增加调度风险的情况下,BSDP-LTF模型相比SDP-I、SDP-LTF模型,可分别减少引水8.2%、4.1%。表明贝叶斯随机动态规划模型BSDP-LTF有效改进了径流描述,提高了跨流域引水的有效性。  相似文献   

一次东北冷涡下槽后强风与飑线后向入流演变及成因分析     

张乐楠  丁治英  王咏青  张璐 《气象科学》2019,39(4):488-501

本文利用NCEP分析资料、多普勒雷达观测资料、常规气象观测资料以及数值模拟结果,对2016年7月30日发生在华北、辽宁附近的一次强飑线过程中后向入流的演变及成因进行研究。结果表明,此次飑线发生在中纬度新生冷涡槽前,低层有水汽辐合区和地面辐合线对应,且过程中伴有较强的对流有效位能释放。飑线后部中层(冷涡槽后)一直存在α中尺度西风大值带,此大风速带造成了上下层相反的水平涡度,并形成喇叭形环流结构,该结构不同于经典飑线结构。飑线后部水平方向上水平涡度分布不均匀,并形成水平涡度旋度上正下负的分布,即导致中层强风区上部上升运动、下部下沉运动,该下沉运动引发飑线中的后向入流和低层强风速带形成。在中层,飑线的后部边缘始终有较强的风速大值带伴随飑线的发展,该大值带的形成与对流强弱和非热成风涡度有关,对流过程中低层非热成风涡度为负,中上层非热成风涡度为正,导致飑线后部中层西风加速和低层西风减速,有利于后向入流的发展和飑线的维持,当对流减弱时,非热成风涡度与后向入流均减弱。文中给出了后向入流形成演变的概念模式。  相似文献   

前倾槽背景下河套地区一次强冰雹天气成因分析     

张桂莲  刘林春  赵斐  于碧新  马素艳  荀学义 《沙漠与绿洲气象(新疆气象)》2019,13(4):1-8

利用常规观测资料、多普勒雷达资料以及NECP(1°×1°)逐6 h再分析资料,对2016年9月22日内蒙古河套地区强冰雹天气成因进行分析,结果表明:在前倾槽有利的天气尺度环流背景下,中高层干冷空气叠加在低层暖湿空气上形成了对流不稳定层结条件。较大的对流有效位能(CAPE)、假相当位温θse高能区、0～6 km中等强度的垂直风切变有利于强冰雹的形成。反射率因子有"钩状回波"、前侧入流缺口、后侧入流缺口;前侧入流缺口表明有上升气流,强盛的上升气流有利于空中大冰雹的增长,后侧入流缺口表明有下沉气流,有可能引起破坏性大风。基本径向速度剖面有明显的中气旋特征,强烈的辐合有利于对流风暴上升运动的进一步发展;对流风暴后侧有辐散下沉气流降落到地面,辐散风出流促使对流风暴前沿的暖湿气流强迫抬升,从而使上升运动得到进一步的加强。反射率因子剖面有弱回波区、回波悬垂且55 dBZ以上的强回波核心位置超过-20℃层等温线高度以上;弱回波区左侧的回波强度高达55～60 dBZ且已经接地,表明有大冰雹降落到地面。  相似文献   

ANALYTICAL HAYAMI SOLUTION FOR THE DIFFUSIVE WAVE FLOOD ROUTING PROBLEM WITH LATERAL INFLOW     

ROGER MOUSSA 《水文研究》1996,10(9):1209-1227

The diffusive wave equation is generally used in flood routing in rivers. The two parameters of the equation, celerity and diffusivity, are usually taken as functions of the discharge. If these two parameters can be assumed to be constant without lateral inflow, the diffusive wave equation may have an analytical solution: the Hayami model. A general analytical method, based on ‘Hayami’s hypothesis, is developed here which resolves the diffusive wave flood routing equation with lateral inflow or outflow uniformly distributed over a channel reach. Flood routing parameters are then identified using observed inflow and outflow and the Hayami model used to simulate outflow. Two examples are discussed. Firstly, the prediction of the hydrograph at a downstream section on the basis of a knowledge of the hydrograph at an upstream section and the lateral inflow. The second example concerns lateral inflow identification between an upstream and a downstream section on the basis of a knowledge of hydrographs at the upstream and downstream sections. The new general Hayami model was applied to flood routing simulation and for lateral inflow identification of the River Allier in France. The major advantages of the method relate to computer simulation, real-time forecasting and control applications in examples where numerical instabilities, in the solution of the partial differential equations must be avoided.  相似文献   

一次模态变异中尺度对流系统的模拟与分析     

汪兰  张述文  柴旺  任星露 《热带气象学报》2022,38(5):671-679

利用NCEP FNL分析资料及南京多普勒雷达观测,借助WRF模式,对2017年8月19日发生在长江中下游地区的一次中尺度对流系统(MCS)进行模拟和诊断分析。此次MCS组织模态PS(Parallel Stratiform)型和TS(Trailing Stratiform)型共存,开始为带状结构,最后演变为强弓状飑线。气旋切变和低空急流是此次过程的重要影响系统,而午后强烈发展的地面锋触发了此次强对流。在垂直风切变和冷池共同作用下,西侧初始对流发展为PS型模态,东侧发展为TS型模态。由于PS型模态的中低层垂直风切变发生转向,导致其消散。TS型模态附近冷池和垂直风切变相配合,且在后向入流(Rear Inflow Jets,RIJ)作用下发展成为强弓状飑线;RIJ受中低层涡旋对影响而发展增强,其中气旋式涡旋主要由涡度方程中拉伸项决定,而反气旋式涡旋则主要由倾侧项决定。  相似文献   

极地低压对费拉姆海峡大西洋入流水天气尺度变化的影响     

孙瑞立  高郭平 《海洋学报(英文版)》2018,37(3):42-50

The Atlantic inflow in the Fram Strait(78°50′N) has synoptic scale variability based on an array of moorings over the period of 1998–2010. The synoptic scale variability of Atlantic inflow, whose significant cycle is 3–16 d, occurs mainly in winter and spring(from January to April) and is related with polar lows in the Barents Sea. On the synoptic scale, the enhancement(weakening) of Atlantic inflow in the Fram Strait is accompanied by less(more)polar lows in the Barents Sea. Wind stress curl induced by polar lows in the Barents Sea causes Ekman-transport,leads to decrease of sea surface height in the Barents Sea, due to geostrophic adjustment, further induces a cyclonic circulation anomaly around the Barents Sea, and causes the weakening of the Atlantic inflow in the Fram Strait. Our results highlight the importance of polar lows in forcing the Atlantic inflow in the Fram Strait and can help us to further understand the effect of Atlantic warm water on the change of the Arctic Ocean.  相似文献   

南海风暴潮对风场和外围海水敏感性研究     

李健  刘清容  阮成卿  訚忠辉  冀承振 《海洋科学》2018,42(2):99-107

为探索来自西北太平洋台风风暴潮与南海局地生成台风风暴潮不同,本研究在假设两种台风气象条件相同情况下,研究随台风而来外围海水所形成增水对南海沿岸的影响。以0814"黑格比"强台风风暴潮为基础,使用ROMS(regional ocean modeling system)模式进行数值模拟并通过设计对比试验方法进行研究,研究发现在台风登陆时引起的增水最大,最大增水出现在台风路径右侧,其中在沿岸区域,外围海水形成增水约占总增水10%,且大约3 h后出现增水回震现象。同时,设计对比试验,研究来自西北太平洋台风风暴潮对台风路径、台风强度、台风移动速度和流入角等气象条件敏感性,并获得与前人一致的结果。  相似文献   

Measurements of Trace Gases in the Inflow of South China Sea Background Air and Outflow of Regional Pollution at Tai O, Southern China     

T. Wang  H. Guo  D. R. Blake  Y. H. Kwok  I. J. Simpson  Y. S. Li 《Journal of Atmospheric Chemistry》2005,52(3):295-317

We present a 16-month record of ozone (O₃), carbon monoxide (CO), total reactive nitrogen (NO_y), sulphur dioxide (SO₂), methane (CH₄), C₂ – C₈ non-methane hydrocarbons (NMHCs), C₁ – C₂ halocarbons, and dimethyl sulfide (DMS) measured at a southern China coastal site. The study aimed to establish/update seasonal profiles of chemically active trace gases and pollution tracers in subtropical Asia and to characterize the composition of the `background' atmosphere over the South China Sea (SCS) and of pollution outflow from the industrialized Pearl River Delta (PRD) region and southern China. Most of the measured trace gases of anthropogenic origin exhibited a winter maximum and a summer minimum, while O₃ showed a maximum in autumn which is in contrast to the seasonal behavior of O₃ in rural eastern China and in many mid-latitude remote locations in the western Pacific. The data were segregated into two groups representing the SCS background air and the outflow of regional continental pollution (PRD plus southern China), based on CO mixing ratios and meteorological conditions. NMHCs and halocarbon data were further analyzed to examine the relationships between their variability and atmospheric lifetime and to elucidate the extent of atmospheric processing in the sampled air parcels. The trace gas variability (S) versus lifetime (τ) relationship, defined by the power law, S_lnx = Aτ^{− b}, (where X is the trace gas mixing ratio) gives a fit parameter A of 1.39 and exponent b of 0.42 for SCS air, and A of 2.86 and b of 0.31 for the regional continental air masses. An examination of ln[n-butane]/ln[ethane] versus ln[propane]/ln[ethane] indicates that their relative abundance was dominated by mixing as opposed to photochemistry in both SCS and regional outflow air masses. The very low ratios of ethyne/CO, propane/ethane and toluene/benzene suggest that the SCS air mass has undergone intense atmospheric processing since these gases were released into the atmosphere. Compared to the results from other polluted rural sites and from urban areas, the large values of these species in the outflow of PRD/southern China suggest source(s) emitting higher levels of ethyne, benzene, and toluene, relative to light alkanes. These chemical characteristics could be unique indicators of anthropogenic emissions from southern China.  相似文献   

副高异常偏西背景下西北一次漏报的雷暴大风中尺度分析*     

姚静  王楠  康磊 《沙漠与绿洲气象(新疆气象)》2020,14(6):10-20

摘要：利用西安多普勒天气雷达、L波段风廓线雷达和加密自动站探测资料，结合天气实况，对2018年7月26日发生在陕西一次副热带高压影响下的的强风暴过程进行了中尺度分析。结果表明：（1）本次强风暴伴随的阵风锋共维持了4h，其中有3h出现7级以上的大风，且最大风力10级。（2）在副热带高压影响下，陕西处于高温、高湿气团中，大气层结极不稳定。（3）此次强风暴在高的对流有效位能环境下（CAPE）下，抬升触发的关键因子是关中地区中尺度辐合线，当初生的对流云团下山后，中尺度辐合线触发的对流风暴形成小范围冷池出流与环境风场形成新的辐合线，加强对流风暴发展。（4）当阵风锋移动过程中遇到前方的对流云团时，将低层暖湿空气抬升，并随着上升气流输送到主体对流风暴中，迅速补充了主体风暴的能量，使得主体风暴再次强烈发展，延长了阵风锋的生命史。  相似文献